Mounting means for knife sharpener stone



May 26, 1970 F. M. HUBRICH 3,513,599

MOUNTING MEANS FOR KNIFE SHARPENER STONE 7 Filed July 20. 1967 2 Sheets-Sheet 1 ATTORN EY May 26, 1970 F. M. HUBRICH 3,513,599

MOUNTING MEANS FOR KNIFE SHARPENER STONE Filed July 20. 1967 2 Sheets-Sheet 2' Ti f 43 I 71 4- ATTORNEY United States Patent 3,513,599 7 MOUNTING MEANS FOR KNIFE SHARPENER STONE Frederick M. Hubrich, Newark, Del., assignor to Ronson Corporation, Woodbridge, N.J., a corporation of New Jerse y Filed July 20, 1967, Ser. No. 654,725

Int. Cl. B24b 3/54 US. Cl. 51-128 3 Claims ABSTRACT OF THE DISCLOSURE A blade sharpening device in which the grinding wheel is mounted on a driven shaft which is within a hollow drive shaft. A slip clutch in the form of a spring clip maintains the driven and driving shafts together. When excessive pressure is applied to the grinding wheel which is mounted on the driven shaft, it slips thereby preventing a blade from being damaged because excess pressure overcomes the spring pressure exerted against a flat on the driven shaft.

This invention relates to a means for mounting a blade grinding stone on a shaft to prevent the blade which is to be sharpened from being burned as the result of applying too much pressure against the grinding stone.

It requires a great deal of skill to sharpen a blade. Since people who are not skilled-in this art attempt to sharpen their cutting blades, numerous devices have been marketed to assist in this task. One of the problems which has been greatly simplified for the neophyte is that of obtaining the proper blade angle. For this, knife sharpeners have been devised having housings against which the blade is seated. The housing is tapered to the optimum cutting angle and the user is thereby assured of the proper angle being placed on the cutting tool. The grinding wheel itself can have the proper angle formed thereon and the knife is held in a vertical position.

Another serious problem confronting the neophyte blade sharpener is that of placing the proper amount of pressure against the grinding wheel with the knife blade. If excessive pressure is placed on the grinding stone by the knife blade the latter can be burned and its effectiveness can be lessened or eliminated entirely.

It is therefore an object of this invention to provide a grinding stone which will stop when a predetermined pressure is placed on it.

It is a further object of this invention to permit rotation of the motor shaft while the grinding stone is stopped thus preventing the motor from being burned out.

It is still a further object of this invention to provide a safe, reliable and inexpensive blade sharpener which can be used by persons unskilled in knife sharpening.

It is another object of this invention to provide an inexpensive and simple to fabricate slip clutch whereby a plurality of shafts can be joined for coextensive rotation and disjointed for relative rotation.

Further objects and advantages will become apparent from the drawings and the following detailed description in which it is my intention to clearly set forth and describe my invention and to show its applicability without limiting its scope. In the drawings and description like reference numerals refer to like parts and:

FIG. 1 is a perspective view showing the inner subassembly removed from the housing;

FIG. 2 is an exploded view showing how the various parts cooperate;

FIG. 3 is a plan view showing elements partly in section;

FIG. 4 is a plan view showing details of the shaft mechanism partly in section;

3,513,599 Patented May 26, 1970 FIG. 5 is a plan view showing the clip in two positions;

FIG. 6 is a partial cut away view showing the latch mechanism in open position;

FIG. 7 is a partial cut away view showing the closed position of the latch; and

FIG. 8 is a plan view taken along the line 88 of FIG. 6.

Referring to FIG. 1, there is shown a housing 10 and an inner subassembly 11 which is received and latched within the housing 10. The housing 10 has a wall 12 hav-. ing an opening 13 therein. The housing 10 includes a second wall 14. Each wall 12 and 14 has a respective land 15 and 16 which extends away from the wall at a 92 degree angle. The wall 12 and the wall 14 are arranged at an angle of approximately degrees included between them; however any other suitable arrangement can be used. This angle permits a device such as scissors to be sharpened. One blade of the scissors is placed against the wall 14 and the flat side of the other blade is laid on the land 15. The land 16 is recessed down from the land 15 to provide clearance to compensate for thickness of the other blade. The scissors is lightly pressed forward to engage sharpening stone 45 which projects into land 15 through aperture 13.

A partition 17 separates knife openings 18 and 19 as seen most clearly in FIG. 3. The openings lead to a sharpening stone to sharpen knife blades. The lower portion of the housing 20 is in the form of a truncated cone and is open at the bottom thereof for the reception of the inner subassembly 11. The housing 10 includes two depending fingers 21 although any number can be used and a bearing 22. The purpose for these elements will be described below.

The inner subassembly 11 comprises a base 23 which can have two openings 24 therein enabling the housing to be secured to a power source. Formed on the base which is preferably a plastic molding, however, any suitable material can be used, is a circular portion 25 having detents 26a and 26b formed in the periphery thereof. The detent 26a is formed to loosely engage the finger 21. The curvature of the detent 26a is gradual and leads to locking detent 26b. Locking detent 26b is formed by an are which is closer to the circumference of the circular portion 25 than the arc 26a. Thus the detent 26a receives the finger 21 and upon rotation of the housing 20 cams the finger 21 into the detent 26b.

Formed integrally with the circular portion 25 is a journal 27 which can include a metal insert therein and includes reinforcing ribs 28 thereon.

Received within the journal 27 is an outer shaft 29. The shaft 29 is hollow for half of its length or at least to a portion past the notch 30 cut therein in the hollow portion of the shaft. The shaft 29 includes a threaded portion 31 thereon and a reduced diameter section 32. The threaded portion 32 is threaded into a mating shaft 33 having a threaded bore 34 therein. The hollow bore 35 of the shaft 33 has grooves 36 milled therein for the reception of a drive shaft of a motor unit (not shown). The motor drive shaft can have splines thereon which frictionally fit into the grooves 36. Any type of frictional engagement can be used between the motor drive shaft and the shaft 33. For example, a hexagonal drive connection could also be used.

Placed within the hollow portion of the shaft 29 is a shaft 37. The shaft 37 includes a reduced diameter section 38 having a flat 39 formed on the surface thereof. The reduced diameter section 38 is located on the shaft 37 so as to be in alignment with the notch 30 when the shaft 37 is assembled within the outer shaft 29. Grooves 40 can be milled into the forward portion of the shaft 37. Instead of grooves this reduced diameter portion could be knurled so as to frictionally receive a conventional grinding Wheel 41. The grinding wheel can be pressed onto the shaft 37 or otherwise fixed thereto. An inner threaded bore 42 at the end of the shaft 37 receives a threaded plug 44 therein. A hexagonal stop 43 locates the plug within the bore 42. The end of the plug 43a is received within the bearing 22 in the housing 10. A second conventional scissors grinding wheel 45 is frictionally fixed to the shaft 37 in the same manner as the grinding wheel 41 and held fast by the plug 44. Washers 46 can be placed on either side of the grinding wheel 41 as separators. A felt washer 47 is frictionally engaged to the shaft 29. The washer 47 prevents bits of metal which have been ground oif blades from entering the notch 30 and the journal 27 which includes a bearing inaert. The shaft 29 is held in the housing 10 by thrust washers 48a and 48b. A spring Washer 49 loosely encircles the shaft 29 and this washer urges the washer 48b gently against the bushing of the bearing 27. The washer 50 on the shaft 29 cooperates with the spring washer 49 to hold the assembly towards an upper position.

The shaft 37 is loosely received within the hollow shaft 29 and is free to rotate therein. Since the shaft 29 is driven directly by the motor, a spring clutch 51 is fitted within the notch 30. The clutch 51 is formed of a resilient rod having a loop therein, a straight arm 51a and a curved arm 51b. The curvature in the arm 51b has approximately the same inner radius as the outer circumference of the shaft 29. Thus, in order to transmit the rotation of the drive shaft 29 to the inner shaft 37 the clutch arm 51a is placed within the notch 30 and the clutch arm 51b is stressed outwardly from ann 51a and engages the shaft 29. The arms 51a and 51!) are resiliently biased apart when placed on the shaft 29 and exert forces on the shafts 29 and 37. When the shaft 37 is placed Within the outer shaft 29 the notch 30 extends through to the inner shaft 37. When the arm 51a of the clutch bears on the fiat 39 on the shaft 37 the rotation of the outer shaft 29 is transmitted through the clutch 51 to the inner shaft 37 and it rotates. Thus, the grinding wheels 41 and 45 fixed to the inner shaft also rotate and a knife blade extending within the slots 18 or 19 or a scissors blade extending within the opening 13 can bear on the respective grinding wheel face which has the proper sharpening angle preformed thereon and be sharpened. If excessive force, such as 1 to 3 ounces, is placed on the grinding wheel, the inner shaft 37 will be held stationary and the outer shaft 29 will slip and the circular portion of the inner shaft 37 will bear against the clutch arm 51a. Since the clutch arm 51a cannot frictionally grip the circular portion of the shaft 37 it will not be driven until the excessive pressure is removed from the grinding wheel. Upon removal of the-excess pressure the outer shaft 29 will rotate with the clutch 51, and when the arm 51a contacts the flattened portion 39 of the shaft 37 it will again drive it and the grinding wheels attached thereto.

The outer housing 10 and the inner housing 11 are assembled by placing the plug 43 which has a bearing surface 43a on the end thereof Within the aligning bearing 22. The depending fingers 21 are then placed Within the detents 26a. The fingers 21 are loosely received within the detents 26a because the inner end of the finger 21 lies on a radius from the center of the base 25 which is greater than the length of the radius to the center of the arc forming the detent 26. By turning the housing 10 clockwise relative to the inner subassembly 11, the fingers 21 are cammed into the detent 26b. The are forming the detent 26b is on a radius which is greater than the radius to the fingers 21; therefore, the fingers 21 which are flexibly mounted are frictionally biased outward, and through their inherent resilience frictionally bear against the detent 26b and maintains the inner subassembly within the outer housing. The assembly 11 is 4 thus easily removed from the housing 10 for repair or cleaning.

The grinding wheel 45 is then properly located Within the housing 10 with respect to the opening 13. The grinding wheel 41 is located with respect to the knife blade openings 18 and 19.

The user places the shaft 33 over the motor drive shaft (not shown) and the unit is put into operation. The user can place a scissors in the open position on the lands 12 and 14 which places the scissors blade in contact with the grinding wheel 45 or a knife blade can be placed in either of the openings 18 and 19 and the blade contacts the grinding wheel 41.

If the user bears down too hard against the grinding wheel 41 or 45 the clutch 51 can no longer transmit the rotation of the shaft 29 to the grinding wheel shaft 37 and no further sharpening will take place until the pressure is removed or diminished. It is therefore impossible for the user to exert too much pressure on a blade.

I claim:

1. In a knife sharpening device comprising,

(a) a base having a journal thereon,

(b) a first hollow rigid shaft journalled on said base for rotation therein,

(c) a second rigid shaft mounted within said first shaft for concentric rotation with said first shaft,

((1) a grinding wheel fixed to said second shaft,

(e) a slip clutch joining said first and second shafts whereby rotation of one of said shafts is transmitted to the other shaft and a predetermined excess pres sure on said grinding wheel will preclude rotation of one of said shafts until the pressure is removed,

(f) a housing removably secured to the base in which said housing has at least one opening therein adjacent to said grinding wheel,

(g) said hollow shaft having a notch therein for the reception of said slip clutch,

(h) said slip clutch comprising a continuous rod formed of resilient material,

(i) said rod being shaped to form overlapping arms which are resiliently biased together to frictionally maintain said first and second shafts joined and said arms being connected by a circular rod portion formed into a loop which extends laterally of the longitudinal axes of said first and second concentric shafts.

2. A knife sharpening device as defined in claim 1 in which,

(a) one arm of said slip clutch engages the first hollow rigid shaft and is removably secured thereto,

(b) the second rigid shaft has a flat portion formed in a portion of its diameter whereby (i) the other arm of said slip clutch removably engages said fiat portion to transmit the rotation of one shaft to the other and to preclude the transmittal of rotation when said slip clutch arm is on the circular portion of the diameter of the rigid shaft.

3. A knife sharpening device comprising,

(a) a housing having at least one opening therein to receive a cutting blade,

(b) a base having a shaft journalled thereon and a grinding wheel fixed to said shaft,

(c) characterized by at least one resilient finger on said housing,

((1) means on said base to frictionally engage said finger and maintain said base and housing locked together,

(i) said means comprising detents on said base and a cam which urges said finger outwardly from its rest position such that the finger locks the housing to the base under the influence of the resilient bias of the finger bearing against one of said detents.

References Cited UNITED STATES PATENTS 2,688,857 9/1954 Jones 64-29 2,722,783 11/1955 ORussa 51-102 Lebus 51-128 X Bednarski 51102 MacFarland 51--102 X Hicks 51128 Wolter 51128 X HAROLD D. WHITEHEAD, Primary Examiner 

